Structural adhesive compositions

ABSTRACT

An adhesive composition comprising an epoxy compound and a compound comprising at least one aminimide functional group is disclosed. The compound comprising the at least one aminimide functional group is present in an amount from 2-8% by weight based on total weight of the adhesive composition and reacts with the epoxy compound upon activation by an external energy source. The adhesive composition also may comprise an amidine salt.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No.14/964,795, filed Dec. 10, 2015, which is incorporated herein byreference.

FIELD

The present invention relates to structural adhesive compositions, andmore particularly to one-component compositions.

BACKGROUND

Structural adhesives are utilized in a wide variety of applications tobond together two or more substrate materials. For example, structuraladhesives may be used for binding together automotive or industrialcomponents.

The present invention is directed towards adhesive compositions thatprovide sufficient bond strength and are easy to apply for use inbonding together substrate materials.

SUMMARY

The present invention also is an adhesive composition comprising anepoxy compound and a polymeric compound comprising at least twoaminimide functional groups, wherein the polymeric compound reacts withthe epoxy compound upon activation by an external energy source; whereinthe polymeric compound is present in an amount from 2-8% by weight basedon total weight of the adhesive composition.

The present invention also is an adhesive composition comprising anepoxy compound and a monomeric compound comprising at least oneaminimide functional group, wherein the monomeric compound reacts withthe epoxy compound upon activation by an external energy source; whereinthe monomeric compound is present in an amount from 2-8% by weight basedon total weight of the adhesive composition.

The present invention also is an adhesive composition comprising anepoxy compound; an aminimide-containing compound present in an amount offrom 2% to 8% by weight based on total weight of the adhesivecomposition; and a reaction product of reactants comprising an amidineand a second component, wherein the epoxy, the aminimide-containingcompound, and the reaction product react upon activation by an externalenergy source.

Also disclosed are adhesives formed from the adhesive compositions andmethods of forming a bonded substrate using the adhesive compositionsdisclosed herein.

DETAILED DESCRIPTION

For purposes of the following detailed description, it is to beunderstood that the invention may assume various alternative variationsand step sequences, except where expressly specified to the contrary.Moreover, other than in any operating examples, or where otherwiseindicated, all numbers such as those expressing values, amounts,percentages, ranges, subranges and fractions may be read as if prefacedby the word “about,” even if the term does not expressly appear.Accordingly, unless indicated to the contrary, the numerical parametersset forth in the following specification and attached claims areapproximations that may vary depending upon the desired properties to beobtained by the present invention. At the very least, and not as anattempt to limit the application of the doctrine of equivalents to thescope of the claims, each numerical parameter should at least beconstrued in light of the number of reported significant digits and byapplying ordinary rounding techniques. Where a closed or open-endednumerical range is described herein, all numbers, values, amounts,percentages, subranges and fractions within or encompassed by thenumerical range are to be considered as being specifically included inand belonging to the original disclosure of this application as if thesenumbers, values, amounts, percentages, subranges and fractions had beenexplicitly written out in their entirety.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard variation found in theirrespective testing measurements.

As used herein, unless indicated otherwise, a plural term can encompassits singular counterpart and vice versa, unless indicated otherwise. Forexample, although reference is made herein to “a” hydrazine comprising atrivalent nitrogen, “an” anhydride functional material, and “a” cyclicester, a combination (a plurality) of these components can be used inthe present invention.

In addition, in this application, the use of “or” means “and/or” unlessspecifically stated otherwise, even though “and/or” may be explicitlyused in certain instances.

As used herein, “including,” “containing” and like terms are understoodin the context of this application to be synonymous with “comprising”and are therefore open-ended and do not exclude the presence ofadditional undescribed or unrecited elements, materials, ingredients ormethod steps. As used herein, “consisting of” is understood in thecontext of this application to exclude the presence of any unspecifiedelement, ingredient or method step. As used herein, “consistingessentially of” is understood in the context of this application toinclude the specified elements, materials, ingredients or method steps“and those that do not materially affect the basic and novelcharacteristic(s)” of what is being described.

As used herein, the terms “on,” “onto,” “applied on,” “applied onto,”“formed on,” “deposited on,” “deposited onto,” mean formed, overlaid,deposited, or provided on but not necessarily in contact with thesurface. For example, an adhesive composition “applied onto” a substratedoes not preclude the presence of one or more other intervening coatinglayers of the same or different composition located between the adhesivecomposition and the substrate.

As used herein, the term “structural adhesive” means an adhesiveproducing a load-bearing joint having a lap shear strength of greaterthan 5 MPa, as determined by using an Instron 5567 machine in tensilemode with a pull rate of 10 mm per minute.

As used herein, “alkyl” refers to an optionally substituted hydrocarbonchain that may be linear or branched.

As used herein, “aromatic” refers to a hydrocarbon having a delocalizedconjugated π-system with alternating double and single bonds betweencarbon atoms forming one or more coplanar hydrocarbon rings.

As used herein, “cycloaliphatic” refers to a hydrocarbon that comprisesone or more hydrocarbon rings that are not aromatic.

As used herein, the term “trivalent nitrogen” refers to a nitrogen atombound to one further nitrogen atom and two carbon atoms.

As defined herein, a “1K” or “one-component” adhesive composition, is acomposition in which all of the ingredients may be premixed and storedand wherein the reactive components do not readily react at ambient orslightly thermal conditions, but instead only react upon activation byan external energy source. In the absence of activation from theexternal energy source, the composition will remain largely unreacted(having less than a 100% increase in viscosity when stored at 25° C. for90 days, where viscosity is measured with an Anton Paar Physica MCR 301rheometer with 25 mm parallel plate and 1 mm gap at the following shearconditions: Conditioning: Rotation with shear rate at 0.1 s⁻¹ for 60seconds; Tempering: No shear for 240 seconds; Amplitude test:Oscillation with log increasing strain γ from 0.01 to 10% in 90 seconds(data measured every 3 seconds); Shear phase: Oscillation with 10%strain (γ) at 10 Hz for 120 seconds (data measured every 10 seconds);Re-conditioning: Rotation with shear rate at 0.1 s⁻¹ for 60 seconds;Regenerated mode: Oscillation with 0.05% strain (γ) for 120 seconds(data measured every 10 seconds)). External energy sources that may beused to promote the curing reaction include, for example, radiation(i.e., actinic radiation such as ultraviolet light) and/or heat. Asfurther defined herein, ambient conditions generally refer to roomtemperature and humidity conditions or temperature and humidityconditions that are typically found in the area in which the adhesive isbeing applied to a substrate, e.g., at 20° C. to 40° C. and 20% to 80%relative humidity, while slightly thermal conditions are temperaturesthat are slightly above ambient temperature but are generally below thecuring temperature for the adhesive composition (i.e., in other words,at temperatures and humidity conditions below which the reactivecomponents will readily react and cure, e.g., >40° C. and less than 100°C. at 20% to 80% relative humidity).

As used herein “monomer” refers generally to a component that can bepolymerized with another polymerizable component such as another monomeror a polymer to form a compound that comprises residues of the monomericor polymeric components, respectively.

As used herein “polymer” refers generally to prepolymers, oligomers,homopolymers, copolymers, or combinations thereof.

As used herein, the term “aminimide” refers to a molecule, i.e. amonomer or polymer, that comprises at least one aminimide functionalgroup. As used herein, an “aminimide functional group” comprises ananionic nitrogen bonded to a cationic nitrogen and a carbonyl groupaccording to the following formula:

wherein R and R′ may be the same or different and may be an alkyl groupor an aryl group. For clarity, an aminimide may comprise functionalgroups in addition to the aminimide functional group(s).

As used herein, the term “carbonyl group” refers to a functional groupcomprising a carbon atom double-bonded to an oxygen atom, which iscommon to several classes of compounds including, but not being limitedto as aldehydes, ketones, carboxylic acids, acid anhydrides, esters,etc.

As used herein, “monofunctional,” when used with respect to the numberof aminimide functional groups a particular monomer or polymercomprises, means a monomer or polymer comprising more than zero (0)aminimide functional groups but fewer than two (2) aminimide functionalgroups, such as, for example, one aminimide group per molecule.

As used herein, “bifunctional,” when used with respect to the number ofaminimide functional groups a particular monomer or polymer comprises,means a monomer or polymer comprising two (2) aminimide functionalgroups per molecule.

As used herein, “polyfunctional,” when used with respect to the numberof aminimide functional groups a particular monomer or polymercomprises, means a monomer or polymer comprising more than two (2)aminimide functional groups per molecule.

As used herein, “aminimide” containing compounds refer to compounds thatact as catalysts for epoxy resins.

As used herein, the term “catalyst” means a substance that increases therate of a chemical reaction without itself undergoing any permanentchemical change.

As used herein, the term “molecular weight” means the theoretical numberaverage molecular weight (M_(n)).

As used herein, unless indicated otherwise, the term “substantiallyfree” means that a particular material is not purposefully added to acomposition and is only present as an impurity in a trace amount of lessthan 1% by weight based on a total weight of the composition. As usedherein, unless indicated otherwise, the term “completely free” meansthat a composition does not comprise a particular material, i.e., thecomposition comprises 0% by weight of such material.

As stated above, disclosed herein is an adhesive composition. Theadhesive composition of the present invention may comprise an epoxycompound and a compound comprising at least one aminimide functionalgroup, wherein the compound comprising the at least one aminimidefunctional group reacts with the epoxy compound upon activation by anexternal energy source, and wherein the compound is present in an amountfrom 2-8% by weight based on total weight of the adhesive composition.

The adhesive composition may comprise an epoxy compound. Suitable epoxycompounds that may be used include monoepoxides, polyepoxides, orcombinations thereof.

Suitable monoepoxides that may be used include monoglycidyl ethers ofalcohols and phenols, such as phenyl glycidyl ether, n-butyl glycidylether, cresyl glycidyl ether, isopropyl glycidyl ether, glycidylversatate, for example, CARDURA E available from Shell Chemical Co., andglycidyl esters of monocarboxylic acids such as glycidyl neodecanoate,and mixtures of any of the foregoing.

Suitable polyepoxides include polyglycidyl ethers of Bisphenol A, suchas Epon® 828 and 1001 epoxy resins, and Bisphenol F diepoxides, such asEpon® 862, which are commercially available from Hexion SpecialtyChemicals, Inc. Other useful polyepoxides include polyglycidyl ethers ofpolyhydric alcohols, polyglycidyl esters of polycarboxylic acids,polyepoxides that are derived from the epoxidation of an olefinicallyunsaturated alicyclic compound, polyepoxides containing oxyalkylenegroups in the epoxy molecule, and combinations thereof.

In addition to the polyepoxides described above, additional polymerscontaining pendant epoxy groups also may be used to form the adhesivecomposition of the present invention. These polymers may be made bycopolymerizing a variety of polymerizable ethylenically unsaturatedmonomers at least one of which is an epoxy containing monomer, e.g.,glycidyl (meth)acrylate or allyl glycidyl ether. An example of such anadditional polymer includes but is not limited to Epon® 1007.

Other useful epoxides that may be used to form the adhesive compositionof the present invention include polyepoxides and are disclosed, forexample, in U.S. Publication No. US 2014/0150970 at paragraphs ?[0023]to [0027], incorporated by reference herein.

Useful polyols that may be used to form an epoxy-functional resin foruse in the adhesive composition include diols, tetraols and higherfunctional polyols. The polyols can be based on a polyether chainderived from ethylene glycol, propylene glycol, butylenes glycol,hexylene glycol and the like and mixtures thereof. The polyol can alsobe based on a polyester chain derived from ring opening polymerizationof caprolactone. Suitable polyols may also include polyether polyol,polyurethane polyol, polyurea polyol, acrylic polyol, polyester polyol,polybutadiene polyol, hydrogenated polybutadiene polyol, polycarbonatepolyols, polysiloxane polyol, and combinations thereof. Polyaminescorresponding to polyols can also be used, and in this case, amidesinstead of carboxylic esters will be formed with acids and anhydrides.

Suitable diols that may be utilized to form the epoxy-functional resinfor use in the adhesive composition are diols having a hydroxylequivalent weight of between 30 and 1000. Exemplary diols having ahydroxyl equivalent weight from 30 to 1000 include diols sold under thetrade name Terathane®, including Terathane® 250, available from Invista.Other exemplary diols having a hydroxyl equivalent weight from 30 to1000 include ethylene glycol and its polyether diols, propylene glycoland its polyether diols, butylenes glycol and its polyether diols,hexylene glycols and its polyether diols, polyester diols synthesized byring opening polymerization of caprolactone, and urethane diolssynthesized by reaction of cyclic carbonates with diamines. Combinationof these diols and polyether diols derived from combination variousdiols described above could also be used. Dimer diols may also be usedincluding those sold under trade names Pripol® and Solvermol™ availablefrom Cognis Corporation.

Polytetrahydrofuran-based polyols sold under the trade name Terathane®,including Terathane® 650, available from Invista, may be used. Inaddition, polyols based on dimer diols sold under the trade namesPripol® and Empol®, available from Cognis Corporation, or bio-basedpolyols, such as the tetrafunctional polyol Agrol 4.0, available fromBioBased Technologies, may also be utilized.

Useful anhydride compounds to functionalize the polyol with acid groupsinclude hexahydrophthalic anhydride and its derivatives (e.g. methylhexahydrophthalic anhydride); phthalic anhydride and its derivatives(e.g. methyl phthalic anhydride); maleic anhydride; succinic anhydride;trimelletic anhydride; pyromelletic dianhydride (PMDA); 3,3′,4,4′-oxydiphthalic dianhydride (ODPA); 3,3′,4,4′-benzopheronetetracarboxylic dianhydride (BTDA); and4,4′-diphthalic(hexamfluoroisopropylidene)anhydride (6FDA). Usefuldiacid compounds to functionalize the polyol with acid groups includephthalic acid and its derivatives (e.g. methyl phthalic acid),hexahydrophthalic acid and its derivatives (e.g. methylhexahydrophthalic acid), maleic acid, succinic acid, adipic acid, etc.Any diacid and anhydride can be used.

According to the present invention, the epoxy compound may be present inthe adhesive composition in an amount of at least 50% by weight based ontotal composition weight, such as at least 60% by weight, such as atleast 70% by weight, and in some cases may be no more than 95% by weightbased on total composition weight, such as no more than 90% by weight,such as no more than 85% by weight. According to the present invention,the epoxy compound may be present in the adhesive composition in anamount from 50% to 95% by weight based on the total composition weight,such as from 60% to 90%, such as from 70% to 87%.

The molecular weight of the epoxy compound may be at least 44, such asat least 58, and in some cases may be no more than 5000, such as no morethan 3000, such as no more than 1000. According to the presentinvention, the molecular weight of the epoxy compound may be from 44 to5000, such as from 58 to 3000, such as from 58 to 1000.

The epoxy compound may have an epoxy equivalent weight (EEW) of at least44, such as at least 58, and in some cases may be no more than 2500,such as no more than 1500, such as no more than 500. According to thepresent invention, the epoxy compound may have an EEW of from 44 to2500, such as from 58 to 1500, such as from 58 to 500. As used herein,EEW refers to the molecular weight of the epoxide compound divided bythe number of epoxy groups per molecule.

The adhesive composition also may comprise a compound containing atleast one aminimide functional group, i.e., the compound may be amonofunctional aminimide, a difunctional aminimide, or a polyfunctionalaminimide. Suitable compounds containing at least one aminimidefunctional group include monomeric or polymeric compounds. Usefulmonomeric aminimide-containing compounds may comprise a reaction productof reactants comprising a monofunctional epoxy and hydrazine with esterfunctionality. Useful polymeric aminimide-containing compounds maycomprise a reaction product of reactants comprising a polymeric epoxy ora polymeric ester with hydrazine. Optionally, the polymeric compound maybe a reaction product of an epoxy compound, a hydrazine and an anhydridefunctional material.

Optionally, the polymeric compound may be a reaction product of an epoxycompound, a hydrazine, and a cyclic compound containing a carbonyl groupand at least one heteroatom alpha to the carbonyl group at a temperaturegreater than 20° C. to form the aminimide-containing material, whereinat least one of the epoxy compound and the cyclic compound is polymeric.

Useful aminimides that may be used in the adhesive composition of thepresent invention are disclosed in U.S. patent application Ser. No.14/964,748, paragraphs ?[0043] to [0056], incorporated herein byreference. For example, useful aminimides include an aminimiderepresented by one of the formulae I-, II, or a combination thereof:

In examples, the aminimide may be formed by reacting an epoxy compound,a hydrazine compound comprising a trivalent nitrogen, and an anhydridefunction material according to at least one of the following reactions:

wherein n≥3; and/or

wherein p≥2.4 and m≥4.3.

According to the present invention, the aminimide may be formed byreacting an epoxy compound, a hydrazine compound comprising a trivalentnitrogen, and a cyclic compound containing a carbonyl group and at leastone heteroatom alpha to the carbonyl group according to at least one ofthe following reactions:

wherein n≥3; and/or

wherein a, b, c, and d each independently are ≥3.

Optionally, the aminimide-containing compound of the present inventionmay comprise at least one functional group in addition to the aminimidefunctional group(s), such as an acid functional group, a hydroxylfunctional group, an amine functional group, a mercaptofunctional group,or combinations thereof.

According to the present invention, the aminimide-containing compoundmay be present in the adhesive composition in an amount of at least 2%by weight based on total weight of the adhesive composition, such as atleast 2.5% by weight, such as at least 3% by weight, and in some casesmay be present in an amount of no more than 8% by weight based on totalweight of the adhesive composition, such as no more than 7.5%, such asno more than 7% by weight. According to the present invention, theaminimide-containing compound may be present in the adhesive compositionin an amount of from 2% to 8% by weight based on total weight of theadhesive composition, such as from 2.5% to 7.5%, such as from 3% to 7%.

According to the present invention, the aminimide-containing compoundmay chemically react with the epoxy compound upon activation by anexternal energy source, such as for example, radiation and/or heat.Optionally, for example, the aminimide-containing compound maychemically react with the epoxy compound upon exposure to a temperatureof at least 100° C., such as at least 110° C., such as at least 120° C.,such as at least 130° C., and in some cases may be exposed to atemperature of no more than 200° C., such as no more than 190° C., suchas no more than 180° C., such as no more than 170° C. According to thepresent invention, the aminimide-containing compound may chemicallyreact with the epoxy compound upon exposure to a temperature of from100° C. to 200° C., such as from 110° C. to 190° C., such as from 120°C. to 180° C., such as from 130° C. to 170° C.

Optionally, in the present invention, the adhesive composition mayfurther comprise a reaction product of reactants comprising an amidineand a second component. Useful amidines include, but are not limited to1,8-diazabicyclo[5.4.0]undec-7-ene; 1,5-diazabicyclo[4.3.0]non-5-ene;1,5,7-triazabicyclo[4.4.0]dec-5-ene; or combinations thereof. Usefulsecond components include but are not limited to a phenol-containingcompound such as for example a phenol formaldehyde resin such as Novolacresins, carbonic acid, a salt of carbonic acid, carbonate, orcombinations thereof. Optionally, in the present invention, the amidineand the second component form an amidine salt. According to the presentinvention, the amidine-containing compound may be present in theadhesive composition in an amount of at least 1% by weight based ontotal weight of the adhesive composition, such as at least 1.25% byweight, such as at least 1.5% by weight, and in some cases may bepresent in an amount of no more than 4% by weight based on total weightof the adhesive composition, such as no more than 3.75%, such as no morethan 3.5% by weight. According to the present invention, theamidine-containing compound may be present in the adhesive compositionin an amount of from 1% to 4% by weight based on total weight of theadhesive composition, such as from 1.25% to 3.75%, such as from 1.5% to3.5%.

Optionally, the adhesive composition also may comprise rubber particleshaving a core-shell structure. Suitable core-shell rubber particles maybe comprised of butadiene rubber or other synthetic rubbers, such asstyrene-butadiene and acrylonitrile-butadiene and the like. The type ofsynthetic rubber and the rubber concentration is not limited as long asthe particle size falls within the specified range as illustrated below.

According to the present invention, the average particle size of therubber particles may be from 0.02 to 500 microns (20 nm to 500,000 nm),for example, the reported particle size for rubber particles provided byKanekea Texas Corporation, as measured by standard techniques known inthe industry, such as, for example, according to ISO 13320 and ISO22412.

According to the present invention, the core-shell rubber particles mayoptionally be included in an epoxy carrier resin for introduction intothe adhesive composition. Suitable finely dispersed core-shell rubberparticles in an average particle size ranging from 50 nm to 250 nm maybe master-batched in epoxy resin such as aromatic epoxides, phenolicnovolac epoxy resin, bisphenol A and/or bisphenol F diepoxide, and/oraliphatic epoxides, which include cyclo-aliphatic epoxides, atconcentrations ranging from 5% to 40% rubber particles by weight basedon the total weight of the rubber dispersion, such as from 20% to 35%.Suitable epoxy resins may also include a mixture of epoxy resins. Whenutilized, the epoxy carrier resin may be an epoxy-containing componentof the present invention such that the weight of the epoxy-containingcomponent present in the structural adhesive composition includes theweight of the epoxy carrier resin.

Exemplary non-limiting commercial core-shell rubber particle productsusing poly(butadiene) rubber particles that may be utilized in theadhesive composition include a core-shell poly(butadiene) rubberdispersion (25% rubber by weight) in bisphenol F (commercially availableas Kane Ace MX 136), a core-shell poly(butadiene) rubber dispersion (33%rubber by weight) in Epon® 828 (commercially available as Kane Ace MX153), a core-shell poly(butadiene) rubber dispersion (37% rubber byweight) in bisphenol A (commercially available as Kane Ace MX 257), anda core-shell poly(butadiene) rubber dispersion (37% rubber by weight) inbisphenol F (commercially available as Kane Ace MX 267), each availablefrom Kaneka Texas Corporation.

Exemplary non-limiting commercial core-shell rubber particle productsusing styrene-butadiene rubber particles that may be utilized in theadhesive composition include a core-shell styrene-butadiene rubberdispersion (33% rubber by weight) in low viscosity bisphenol A(commercially available as Kane Ace MX 113), a core-shellstyrene-butadiene rubber dispersion (25% rubber by weight) in bisphenolA (commercially available as Kane Ace MX 125), a core-shellstyrene-butadiene rubber dispersion (25% rubber by weight) inD.E.N.™-438 phenolic novolac epoxy (commercially available as Kane AceMX 215), a core-shell styrene-butadiene rubber dispersion (25% rubber byweight) in Araldite® MY-721 multi-functional epoxy (commerciallyavailable as Kane Ace MX 416), a core-shell styrene-butadiene rubberdispersion (25% rubber by weight) in MY-0510 multi-functional epoxy(commercially available as Kane Ace MX 451), a core-shellstyrene-butadiene rubber dispersion (25% rubber by weight) in Syna Epoxy21 Cyclo-aliphatic Epoxy from Synasia (commercially available as KaneAce MX 551), and a core-shell styrene-butadiene rubber dispersion (25%rubber by weight) in polypropylene glycol (MW 400) (commerciallyavailable as Kane Ace MX 715), each available from Kaneka TexasCorporation.

According to the present invention, if rubber particles having acore-shell structure are included in the adhesive composition, therubber particles may be present in the adhesive composition in an amountof at least 10% by weight based on total composition weight, such as atleast 20% by weight, such as at least 25% by weight, and in some casesmay be present in the adhesive composition in an amount of no more than45% by weight based on total composition weight, such as no more than40% by weight, such as no more than 35% by weight. According to thepresent invention, rubber particles having a core-shell structure may bepresent in the adhesive composition, if at all, in an amount of from 10%to 45% by weight based on the total composition weight, such as from 20%to 40% by weight, such as from 25% to 35% by weight.

According to the present invention, the adhesive composition optionallymay further comprise a secondary latent curing catalyst to promote thereaction of the epoxy compound and the polymeric compound. Usefulsecondary latent curing catalysts may be imidazoles such as2,4-diamino-6-[2′-methylimidazolyl-(1′)]-ethyl-s-triazine (commerciallyavailable as Curezol® 2MZ Azine, Air Products and Chemicals, Inc.,Allentown, Pa.) or2,4-diamino-6-[2′-methylimidazolyl-(1′)]-ethyl-s-triazineisocyanuricacid adduct dihydrate (commercially available as Curezol® 2MA-OK, AirProducts and Chemicals, Inc., Allentown, Pa.), dicyandiamide (also knownas Dyhard®, available from AlzChem AG, Trostberg, Germany),3,4-dichlorophenyl-N,N-dimethylurea (also known as Diuron, availablefrom AlzChem AG, Trostberg, Germany), or combinations thereof.

According to the present invention, when utilized, the secondary latentcuring catalyst may be present in the structural adhesive in an amountof at least 1% by weight based on total composition weight, such as atleast 2% such as at least 3%, and in some cases may be present in theadhesive composition in an amount of no more than 5% by weight based ontotal composition weight, such as no more than 4.5%, such as no morethan 3.5%. According to the present invention, the secondary latentcuring catalyst, if present, may present in an amount of from 1% to 5%by weight based on total composition weight, such as from 2% to 4.5%,such as from 3% to 3.5%.

Optionally, the adhesive formulation may also include epoxy compounds orresins that are not incorporated into or reacted as a part of any of thecomponents described above, including epoxy-functional polymers that canbe saturated or unsaturated, cyclic or acyclic, aliphatic, alicyclic,aromatic or heterocyclic. The epoxy-functional polymers can have pendantor terminal hydroxyl groups, if desired. They can contain substituentssuch as halogen, hydroxyl, and ether groups. A useful class of thesematerials includes polyepoxides comprising epoxy polyethers obtained byreacting an epihalohydrin (such as epichlorohydrin or epibromohydrin)with a di- or polyhydric alcohol in the presence of an alkali. Suitablepolyhydric alcohols include polyphenols such as resorcinol; catechol;hydroquinone; bis(4-hydroxyphenyl)-2,2-propane, i.e., Bisphenol A;bis(4-hydroxyphenyl)-1,1-isobutane; 4,4-dihydroxybenzophenone;bis(4-hydroxyphenol)-1,1-ethane; bis(2-hydroxyphenyl)-methane and1,5-hydroxynaphthalene.

Frequently used polyepoxides include polyglycidyl ethers of Bisphenol A,such as Epon® 828 epoxy resin which is commercially available fromHexion Specialty Chemicals, Inc. and having a number average molecularweight of about 400 and an epoxy equivalent weight of about 185-192.Other useful polyepoxides include polyglycidyl ethers of otherpolyhydric alcohols, polyglycidyl esters of polycarboxylic acids,polyepoxides that are derived from the epoxidation of an olefinicallyunsaturated alicyclic compound, polyepoxides containing oxyalkylenegroups in the epoxy molecule, epoxy novolac resins, and polyepoxidesthat are partially defunctionalized by carboxylic acids, alcohol, water,phenols, mercaptans or other active hydrogen-containing compounds togive hydroxyl-containing polymers.

According to the present invention, reinforcement fillers may be addedto the adhesive composition. Useful reinforcement fillers that may beintroduced to the adhesive composition to provide improved mechanicalproperties include fibrous materials such as fiberglass, fibroustitanium dioxide, whisker type calcium carbonate (aragonite), and carbonfiber (which includes graphite and carbon nanotubes). In addition, fiberglass ground to 5 microns or wider and to 50 microns or longer may alsoprovide additional tensile strength. Such reinforcement fillers, ifutilized, may be present in the adhesive composition in an amount of atleast 0.1% by weight based on total composition weight, such as at least0.5% by weight, such as at least 1% by weight and, in some cases, may bepresent in an amount of no more than 5% by weight based on totalcomposition weight, such as no more than 4.5% by weight, such as no morethan 4% by weight. According to the present invention, reinforcementfillers may be present in the adhesive composition in an amount of from0.1% by weight to 5% by weight based on total composition weight, suchas from 0.5% by weight to 4.5% by weight, such as from 1% by weight to4% by weight.

Optionally, according to the present invention, additional fillers,thixotropes, colorants, tints and/or other materials also may be addedto the adhesive composition.

Useful thixotropes that may be used include untreated fumed silica andtreated fumed silica, Castor wax, clay, and organo clay. In addition,fibers such as synthetic fibers like aromatic polyamide fibers (such asthose commercially available as Aramid® fiber and Kevlar® fiber),acrylic fibers, and engineered cellulose fiber may also be utilized.

Useful colorants or tints may include red iron pigment, titaniumdioxide, calcium carbonate, phthalocyanine green and phthalocyanineblue.

Useful fillers that may be used in conjunction with thixotropes mayinclude inorganic fillers such as inorganic clay or silica.

Exemplary other materials that may be utilized include, for example,calcium oxide and carbon black.

The adhesive composition of the present invention may consistessentially of, or in some cases may consist of, an epoxy compound and apolymeric compound comprising at least two aminimide functional groups,wherein the polymeric compound reacts with the epoxy compound uponactivation by an external energy source; wherein the polymeric compoundis present in an amount from 2-8% by weight based on total weight of theadhesive composition.

The adhesive composition of the present invention may consistessentially of, or in some cases may consist of, an epoxy compound and amonomeric compound comprising at least one aminimide functional group,wherein the monomeric compound reacts with the epoxy compound uponactivation by an external energy source; wherein the monomeric compoundis present in an amount from 2-8% by weight based on total weight of theadhesive composition.

The adhesive composition of the present invention may comprise, or insome cases may consist essentially of, or in some cases may consist of,an adhesive composition comprising an epoxy compound, anaminimide-containing compound present in an amount of from 2% to 8% byweight based on total weight of the adhesive composition, and a reactionproduct of reactants comprising an amidine and a second component,wherein the epoxy, the aminimide-containing compound, and the reactionproduct react upon activation by an external energy source.

The present invention may also be a method for preparing an adhesivecomposition comprising, or in some cases consisting of, or in some casesconsisting essentially of, mixing an epoxy and a compound comprising atleast one aminimide functional group. According to the presentinvention, the epoxy compound may be any of the monoepoxides orpolyepoxides described above. According to the present invention, thecompound comprising the at least one aminimide functional group may bemonomeric or polymeric, as described above, and may have at least oneaminimide functional groups, as described above.

As stated above, the present disclosure is directed to one-componentstructural adhesive compositions that are used to bond together twosubstrate materials for a wide variety of potential applications inwhich the bond between the substrate materials provides particularmechanical properties related to elongation, tensile strength, lap shearstrength, T-peel strength, modulus, or impact peel strength. Thestructural adhesive may be applied to either one or both of thesubstrate materials being bonded such as, by way of non-limitingexample, components of an automobile frame. The pieces are aligned, andpressure and spacers may be added to control bond thickness. Theadhesive may be cured using an external source such as an oven (or otherthermal means) or through the use of actinic radiation (UV light, etc.).Suitable substrate materials that may be bonded by the structuraladhesive compositions of the present invention include, but are notlimited to, materials such as metals or metal alloys, natural materialssuch as wood, polymeric materials such as hard plastics, or compositematerials wherein each of the first and the second substrate materialmay be independently selected from these materials. The structuraladhesives of the present invention are particularly suitable for use invarious automotive or industrial applications.

The present invention may also be a method for forming a bondedsubstrate comprising, or in some cases consisting of, or in some casesconsisting essentially of, applying the adhesive composition describedabove to a first substrate; contacting a second substrate to theadhesive composition such that the adhesive composition is locatedbetween the first substrate and the second substrate; and curing theadhesive composition.

The adhesive composition described above may be applied alone or as partof an adhesive system that can be deposited in a number of differentways onto a number of different substrates. The adhesive system maycomprise a number of the same or different adhesive layers. An adhesivelayer is typically formed when an adhesive composition that is depositedonto the substrate is at least partially cured by methods known to thoseof ordinary skill in the art (e.g., by exposure to thermal heating).

The adhesive composition can be applied to the surface of a substrate inany number of different ways, non-limiting examples of which includebrushes, rollers, films, pellets, spray guns and applicator guns.

After application to the substrate, the adhesive composition can be atleast partially cured, such as by baking and/or curing at elevatedtemperature for any desired time period sufficient to at least partiallycure the adhesive composition on the substrate (e.g., from 5 minutes to1 hour), such as at a temperature of at least 100° C., such as at least110° C., such as at least 120° C., such as at least 130° C., and in somecases may be exposed to a temperature of no more than 200° C., such asno more than 190° C., such as no more than 180° C., such as no more than170° C. According to the present invention, the adhesive composition canbe at least partially cured, such as by baking and/or curing at elevatedtemperature for any desired time period sufficient to at least partiallycure the adhesive composition on the substrate (e.g., from 5 minutes to1 hour), such as at a temperature of from 100° C. to 200° C., such asfrom 110° C. to 190° C., such as from 120° C. to 180° C., such as from130° C. to 170° C.

It was surprisingly discovered that the adhesive composition of thepresent invention resulted in improved stability of the composition, asdemonstrated by improved complex viscosity, as well as improvedmechanical properties of the cured adhesive, such as improved lap shear.

The adhesive composition of the present invention (as measured with anAnton Paar Physica MCR 301 rheometer with 25 mm parallel plate and 1 mmgap) may have a change in complex viscosity (η*A1, measured at thecondition of γ=0.05% (at 21 seconds) after 3 days at 43° C. (conditionedat 35° C. before each measurement)) of no more than 5× the initialvalue, such as no more than 4× the initial value, such as no more than3× the initial value, such as no more than 2× the initial value.

According to the present invention, after the adhesive composition isapplied to a substrate and at least partially cured, the bondedsubstrate(s) may demonstrate a lap shear of at least 7 as measuredaccording to ISO 4587 test method, such as at least 12, such as at least14, such as at least 16, such as at least 22.

Whereas particular embodiments have been described above for purposes ofillustration, it will be evident to those skilled in the art thatnumerous variations of the details of the coating composition, coating,and methods disclosed herein may be made without departing from thescope in the appended claims.

Illustrating the invention are the following examples that are not to beconsidered as limiting the invention to their details. All parts andpercentages in the examples, as well as throughout the specification,are by weight unless otherwise indicated.

EXAMPLES

The following Examples A-J provide descriptions of the synthesis ofaminimide-containing materials and 1,8-diazabicyclo[5.4.0]undec-7-ene(DBU) salts which were used to prepare the adhesive compositions ofExamples 2-12, as described in further detail herein. In each Example,the final powder was ground with a mortar and pestle, and was shaken ona sieve shaker (Retsch AS 300) at an amplitude of 1 mm/g and a sieve of<125 μm.

Synthesis Examples A-J Example A

Compound A was synthesized as follows: Into a 500-milliliter, 4-neckedflask equipped with a stirrer, a condenser, a nitrogen inlet, and athermocouple in a heating mantle, was charged 68.0 grams of methylbenzoate, 50.06 grams of 1,1-dimethylhydrazine (62% by weight solutionavailable from Lonza Group Ltd.), 31.6 grams of propylene oxide, and 310grams of isopropanol. Agitation and a nitrogen flow of 0.2 scft/min(“scft” means standard cubic feet) were started. The mixture was stirredat 20° C. for 2 hours and then at 55° C. for 24 hours. The reactionprogress was monitored by a Gas Chromatographer. After completion of thereaction, the reaction mixture was concentrated by evaporation ofsolvent, and the residual white solid was recrystallized from ethylacetate. A white powder was obtained in a yield of 56% by weight. Thesolid was further ground into fine powder having a sieve fraction of<125 μm as described above.

Example B

Into a 500-milliliter, 4-necked flask equipped with a stirrer, acondenser, a nitrogen inlet, and a thermocouple in a heating mantle, wascharged 54.4 grams of methyl benzoate, 40.6 grams of 1-aminopiperidine,23.21 grams of propylene oxide, and 250 grams of isopropanol. Agitationand a nitrogen flow of 0.2 scft/min (“scft” means standard cubic feet)were started. The mixture was stirred at 20° C. for 2 hours and then at55° C. for 24 hours. The reaction progress was monitored by a GasChromatographer. After completion of the reaction, the reaction mixturewas concentrated by evaporation of solvent, and the residual white solidwas recrystallized from ethyl acetate. A white powder was obtained in ayield of 59% by weight. The solid was further ground into fine powderhaving a sieve fraction of <125 μm, as described above.

Example C

Into a 500-milliliter, 4-necked flask equipped with a stirrer, acondenser, a nitrogen inlet, and a thermocouple in a heating mantle, wascharged 54.4 grams of dimethyl terephthalate, 54.31 grams of1,1-dimethylhydrazine (62% solution), 65.09 grams of propylene oxide,and 203 grams of isopropanol. Agitation and a nitrogen flow of 0.2scft/min (“scft” means standard cubic feet) were started. The mixturewas stirred at 20° C. for 2 hours and then at 80° C. for 8 hours. Thereaction progress was monitored by a Gas Chromatographer. Aftercompletion of the reaction, the reaction mixture was concentrated byevaporation of solvent, and the residual white solid was recrystallizedfrom ethyl acetate. A white powder was obtained in a yield of 48% byweight. The solid was further ground into fine powder having a sievefraction of <125 μm, as described above.

Example D

Into a 500-milliliter, 4-necked kettle equipped with a stirrer, acondenser, a nitrogen inlet, and a thermocouple in a heating mantle, wascharged 30.0 grams of methyl benzoate, 22.07 grams of1,1-dimethylhydrazine (62% solution), 137.4 grams of Epon 1001 (75% inxylene available from Momentive Performance Materials Inc.), and 130grams of Dowanol PM. Agitation and a nitrogen flow of 0.2 scft/min(“scft” means standard cubic feet) were started. The mixture was stirredat 20° C. for 1 hour, and at 55° C. for 4 hours, and then 80° C. for 16hours. The reaction progress was monitored by a Gas Chromatographer.After completion of the reaction, the reaction mixture was concentratedby evaporation of solvent under vacuum. The residual liquid was pouredout onto aluminum foil and formed a solid at room temperature. The solidwas ground into fine powder having a sieve fraction of <125 μm, asdescribed above.

Example E

Into a 500-milliliter, 4-necked kettle equipped with a stirrer, acondenser, a nitrogen inlet, and a thermocouple in a heating mantle, wascharged 25.81 grams of 1,1-dimethylhydrazine (62% solution), 238.5 gramsof Epon 1001 (75% in xylene), and 100 grams of isopropanol and 20 gramsof Dowanol PM. Agitation and a nitrogen flow of 0.2 scft/min (“scft”means standard cubic feet) were started. The mixture was stirred at 20°C. for 1 hour, and at 55° C. for 5 hours. The reaction progress wasmonitored by amine MEQ (as determined by ASTM D4370, using 716 DMSTitrino from Brinkmann). When amine MEQ stalled, 41.0 grams ofhexahydrophthalic anhydride (HHPA) were added into reaction mixture. Thereaction mixture was heated to 80° C. until anhydride peaks (1857 cm⁻¹and 1782 cm⁻¹) disappeared in the IR spectrum of the reaction mixture.After completion of the reaction, the reaction mixture was concentratedby evaporation of solvent under vacuum. The residual liquid was pouredout onto aluminum foil and formed a solid at room temperature. The solidwas ground into fine powder having a sieve fraction of <125 μm, asdescribed above.

Example F

Into a 500-milliliter, 4-necked kettle equipped with a stirrer, acondenser, a nitrogen inlet, and a thermocouple in a heating mantle, wascharged 25.81 grams of 1,1-dimethylhydrazine (62% solution), 238.5 gramsof Epon 1001 (75% in xylene), and 103 grams of Dowanol PM. Agitation anda nitrogen flow of 0.2 scft/min (“scft” means standard cubic feet) werestarted. The mixture was stirred at 20° C. for 1 hour, and at 80° C. for8 hours. The reaction progress was monitored by amine MEQ. When amineMEQ stalled, 30.3 grams of e-caprolactone were added into reactionmixture at 50° C. After addition, the reaction mixture was heated to 80°C. until e-caprolactone peaks (850 cm⁻¹ and 860 cm⁻¹) disappeared in theIR spectrum of the reaction mixture. After completion of the reaction,the reaction mixture was concentrated by evaporation of solvent undervacuum. The residual liquid was poured out onto aluminum foil and formeda solid at room temperature. The solid was ground into fine powderhaving a sieve fraction of <125 μm, as described above.

Example G

Into a 500-milliliter, 4-necked kettle equipped with a stirrer, acondenser, a nitrogen inlet, and a thermocouple in a heating mantle, wascharged 51.20 grams of methyl trimethyl acetate, 44.30 grams of1,1-dimethylhydrazine (62% solution), 275.60 grams of Epon 1001 (75% inxylene), and 160 grams of Dowanol PM. Agitation and a nitrogen flow of0.2 scft/min (“scft” means standard cubic feet) were started. Themixture was stirred at 20° C. for 1 hour, and at 55° C. for 2 hours, andthen 80° C. for 12 hours. The reaction progress was monitored by a GasChromatographer. After completion of the reaction, the reaction mixturewas concentrated by evaporation of solvent under vacuum. The residualliquid was poured out onto aluminum foil and formed a solid at roomtemperature. The solid was ground into fine powder having a sievefraction of <125 μm, as described above.

Example H

Into a 500-milliliter, 4-necked kettle equipped with a stirrer, acondenser, a nitrogen inlet, and a thermocouple in a heating mantle, wascharged 32.31 grams of 1,1-dimethylhydrazine (62% solution), 19.36 gramsof propylene oxide, and 61.40 grams of Dowanol PM. Agitation and anitrogen flow of 0.2 scft/min (“scft” means standard cubic feet) werestarted. The mixture was stirred at 20° C. for 1 hour, and at 50° C. for5 hours. The reaction progress was monitored by amine MEQ. When amineMEQ stalled, 147.5 grams of maleic anhydride octadecene copolymer (solid71%) were added into reaction mixture at 50° C. After addition, thereaction mixture was heat to 80° C. until anhydride peaks (1857 cm⁻¹ and1782 cm⁻¹) disappeared by IR. After completion of the reaction, and thereaction mixture was concentrated by evaporation of solvent undervacuum. The residual liquid was poured out onto aluminum foil and formeda solid at room temperature. The solid was ground into fine powderhaving a sieve fraction of <125 μm, as described above.

Example I

Into a 500-milliliter, 4-necked kettle equipped with a stirrer, acondenser, a nitrogen inlet, and a thermocouple in a heating mantle, wascharged 165.0 grams of FRJ-425 (a phenol formaldehyde novolac resincommercially available from SI Group) and heated to 160° C. to become aliquid. 117.6 grams of DBU (Industrial grade from BASF) were added intoreaction mixture drop wise. After addition, the reaction mixture washeated to 180° C. and held for 30 minutes. After holding, the liquid waspoured out onto aluminum foil and formed a solid at room temperature.The solid was ground into fine powder having a sieve fraction of <125μm, as described above.

Example J

Into a 2000-milliliter, 4-necked kettle equipped with a stirrer, acondenser, a nitrogen inlet, and a thermocouple, was charged 50.6 gramsof DBU (Industrial grade from BASF), 6.66 grams of DI water, and 300grams of ethyl acetate. 50 grams of dry ice were partially added intoreaction mixture and white precipitate formed. After addition, thereaction mixture was held at room temperature for 1 hour. After holding,the white solid was collected by filtration. The solid was washed withethyl acetate twice (2×30 mL) and dried in vacuum oven. A white powderwas obtained in a yield of 97% by weight. The solid was ground into finepowder having a sieve fraction of <125 μm, as described above.

The following examples show the preparation of various adhesivecompositions prepared with aminimides of the invention as catalysts forepoxy resins. Components were added in the order shown in Table 1.

Adhesive Examples 1-12

Twelve (12) adhesive compositions were prepared from the mixture ofingredients shown in Table 1.

TABLE 1 Adhesive compositions Components Ex. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5Ex. 6 Ex. 7 Ex. 8 Ex. 9 Ex. 10 Ex. 11 Ex. 12 Kane Ace MX-153¹ 48 48 4848 48 48 48 48 48 48 48 48 Epoxy resin² 18.4 18.4 18.4 18.4 18.4 18.418.4 18.4 18.4 18.4 18.4 18.4 TINT-AYD ST 8703³ 0.1 0.1 0.1 0.1 0.1 0.10.1 0.1 0.1 0.1 0.1 0.1 Dyhard SF100⁴ 3.4 3.4 3.4 3.4 3.4 3.4 3.4 3.43.4 3.4 3.4 3.4 Diuron⁵ 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3Synthesis Example A — 2 — — — — — — — 2 2 — Synthesis Example B — — 2 —— — — — — — — — Synthesis Example C — — — 2 — — — — — — — — SynthesisExample D — — — — 4 — — — — — — — Synthesis Example E — — — — — 4 — — —— — Synthesis Example F — — — — — — 4 — — — — — Synthesis Example G — —— — — — — 4 — — — — Synthesis Example H — — — — — — — — 4 — — 4Synthesis Example I — 2 2 2 2 2 2 2 2 — — — Synthesis Example J — — — —— — — — — 2 — — Mica⁶ 1 1 1 1 1 1 1 1 1 1 1 1 Calcium Oxide⁷ 2 2 2 2 2 22 2 2 2 2 2 TOTAL 73.2 77.2 77.2 77.2 79.2 79.2 79.2 79.2 79.2 77.2 75.277.2 ¹Blend of bisphenol A based epoxy resin and core-shell rubberavailable from Kaneka Corporation ²Epoxy capped polyester ³Phthalo greendye available from Elementis Specialties ⁴Cyanoguanidine available fromAlz Chem ⁵Dimethyl-1,1,3-(3,4-dichlorophenyl) available from Alz Chem⁶Potassium alumina silica available from Pacer Corporation ⁷Availablefrom Mississippi Lime Company

Adhesive lap shear specimens were prepared by applying adhesive on 20mm×90 mm×0.8 mm size of hot dip galvanized (HDG) steel panels. Theadhesive was applied to one end of a panel covering the whole width and10 mm from the end. Glass beads with an average diameter of 0.25 mm werelightly sprinkled onto the adhesive to help maintain thickness. Anotherpanel without adhesive was then placed over the adhesive area in anend-to-end fashion that would result in a 10 mm×20 mm bond area. Thejoints were secured with metal clips with excess adhesive cleaned. Theywere then placed in an oven and baked according to specifications. Thebaked adhesive specimens were tested in an Instron 5567 machine intensile mode with a pull rate of 10 mm per minute.

The adhesive lap shear strengths for the above compositions are shown inTable 2.

TABLE 2 Lap Shear Lap shear Tensile (MPa) Ex. Ex. Ex. Bake condition Ex.1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 10 11 12 130° C./ 3.418.2 18.4 17.6 18.2 19.2 18.1 17.4 13.2 19.7 7.3 14.4 17 minutes

Adhesive viscosity was measured with an Anton Paar Physica MCR 301rheometer with 25 mm parallel plate and 1 mm gap. Shear condition forthe measurement was as follows: Conditioning: Rotation with shear rateat 0.1 s⁻¹ for 60 seconds; Tempering: No shear for 240 seconds;Amplitude test: Oscillation with log increasing strain γ from 0.01 to10% in 90 seconds (data measured every 3 seconds); Shear phase:Oscillation with 10% strain (γ) at 10 Hz for 120 seconds (data measuredevery 10 seconds); Re-conditioning: Rotation with shear rate at 0.1 s⁻¹for 60 seconds; Regenerated mode: Oscillation with 0.05% strain (γ) for120 seconds (data measured every 10 seconds).

Complex viscosity η*A1, measured at the condition of γ=0.05% (at 21seconds), of the above adhesives was measured for its initial value,after 3 days at 43° C. Samples were conditioned to 35° C. before eachmeasurement. Results of those measurements are shown in Table 3.

TABLE 3 Viscosity Complex viscosity η* A1 Ex. Ex. Ex. Aging ConditionEx. 1 Ex. 2 Ex. 3 Ex. 4 Ex. 5 Ex. 6 Ex. 7 Ex. 8 Ex. 9 10 11 12 Initial583 634 634 774 689 665 1190 710 772 846 584 716 3 days at 43° C. 594829 799 1270 3770 810 1120 3480 2170 2290 732 1770

ASPECTS OF THE INVENTION

In the following, some aspects of the invention are summarized:

1. An adhesive composition comprising:

an epoxy compound; and

a compound comprising at least one aminimide functional group, whereinthe compound comprising at least one aminimide functional group reactswith the epoxy compound upon activation by an external energy source;wherein the compound comprising at least one aminimide functional groupis present in an amount from 2-8% by weight based on total weight of theadhesive composition.

2. The adhesive composition of aspect 1 comprising:

an epoxy compound; and

a polymeric compound comprising at least two aminimide functionalgroups, wherein the polymeric compound reacts with the epoxy compoundupon activation by an external energy source; wherein the polymericcompound is present in an amount from 2-8% by weight based on totalweight of the adhesive composition.

3. The adhesive composition of aspect 2, wherein the polymeric compoundcomprises a reaction product of reactants comprising a polyepoxide, ahydrazine comprising a trivalent nitrogen, and a reactant comprising acarbonyl group.

4. The adhesive composition of aspect 2 or 3, wherein the polymericcompound further comprises at least one additional functional group.

5. The adhesive composition of aspect 1 comprising:

an epoxy compound; and

a monomeric compound comprising at least one aminimide functional group,wherein the monomeric compound reacts with the epoxy compound uponactivation by an external energy source; wherein the monomeric compoundis present in an amount from 2-8% by weight based on total weight of theadhesive composition.

6. The adhesive composition of aspect 5, wherein the monomeric compoundcomprises a reaction product of reactants comprising a monoepoxide, ahydrazine comprising a trivalent nitrogen, and a reactant comprising acarbonyl group.

7. The adhesive composition of any of the preceding aspects, wherein theepoxy compound is present in an amount of from 50% to 90% by weightbased on total composition weight.

8. The adhesive composition of any of the preceding aspects, wherein theepoxy contains an epoxy-capped polyester.

9. The adhesive composition of any of the preceding aspects, furthercomprising an amidine salt.

10. The adhesive composition of any of the preceding aspects, whereinthe external energy source comprises a temperature of at least 100° C.

11. The adhesive composition of aspect 1 comprising:

an epoxy compound;

an aminimide-containing compound present in an amount of from 2% to 8%by weight based on total weight of the adhesive composition; and

a reaction product of reactants comprising an amidine and a secondcomponent,

wherein the epoxy, the aminimide-containing compound, and the reactionproduct react upon activation by an external energy source.

12. The adhesive composition of aspect 11, wherein the aminimide is areaction product of a polyepoxide and/or a monoepoxide, a hydrazinecomprising a trivalent nitrogen, and a reactant comprising a carbonylgroup.

13. The adhesive composition of aspect 11 or 12, wherein the secondcomponent comprises a phenol.

14. The adhesive composition of any of aspects 11-13, wherein the secondcomponent comprises carbonic acid, a salt of carbonic acid, carbonate,or combinations thereof.

15. The adhesive composition of any of the preceding aspects, furthercomprising rubber particles having a core/shell structure.

16. The adhesive composition of any of the preceding aspects, furthercomprising a secondary latent catalyst.

17. A method for forming a bonded substrate comprising:

applying the adhesive composition of any of the preceding aspects to afirst substrate;

contacting a second substrate to the adhesive composition such that theadhesive composition is located between the first substrate and thesecond substrate; and

curing the adhesive composition.

18. An adhesive comprising the composition of any of the precedingaspects in a cured state.

It will be appreciated by skilled artisans that numerous modificationsand variations are possible in light of the above disclosure withoutdeparting from the broad inventive concepts described and exemplifiedherein. Accordingly, it is therefore to be understood that the foregoingdisclosure is merely illustrative of various exemplary aspects of thisapplication and that numerous modifications and variations can bereadily made by skilled artisans which are within the spirit and scopeof this application and the accompanying claims.

We claim:
 1. An adhesive composition comprising: an epoxy compound; apolymeric compound comprising at least two aminimide functional groups,wherein the polymeric compound reacts with the epoxy compound uponexposure to a temperature of at least 100° C.; wherein the polymericcompound is present in an amount of 2-8% by weight based on total weightof the adhesive composition; rubber particles having a core/shellstructure; and a secondary latent catalyst; wherein the compositioncomprises a one-component composition and has less than a 100% increasein viscosity when stored at 25° C. for 90 days.
 2. The adhesivecomposition of claim 1, wherein the epoxy compound is present in anamount of 50% to 90% by weight based on total composition weight.
 3. Theadhesive composition of claim 1, wherein the epoxy comprises anepoxy-capped polyester.
 4. The adhesive composition of claim 1, whereinthe polymeric compound comprises a reaction product of reactantscomprising a polyepoxide, a hydrazine comprising a trivalent nitrogen,and a reactant comprising a carbonyl group.
 5. The adhesive compositionof claim 1, wherein the polymeric compound further comprises at leastone additional functional group.
 6. The adhesive composition of claim 1,further comprising an amidine salt.
 7. A method for forming a bondedsubstrate comprising: applying the adhesive composition of claim 1 to afirst substrate; contacting a second substrate to the adhesivecomposition such that the adhesive composition is located between thefirst substrate and the second substrate; and curing the adhesivecomposition.
 8. An adhesive comprising the composition of claim 1 in acured state.
 9. The adhesive composition of claim 1, wherein the atleast two aminimide functional groups comprise an anionic nitrogenbonded to a cationic nitrogen and a carbonyl group.
 10. The adhesivecomposition of claim 1, wherein the at least two aminimide functionalgroups comprise the formula

wherein R and R′ may be the same or different and may be an alkyl groupor an aryl group.